An inverted index is a data structure that consists of a list of all unique words and list of the documents in which it appears. New documents are analyzed and then stored as inverted indexes, to allow very fast full-text searches.
Analysis is the process of converting the text into tokens and normalizing tockens before adding them into an inverted index. When we do a full text search, we search the inverted index rather than on the actual documents. So both the indexed text and the query string must be analyzed.